The present invention is directed to signal amplifiers used with a sensor such as a read head in an information storage device, and especially to such signal amplifiers for which some control is available regarding certain operating parameters associated with the amplifier.
There are many important goals in designing and operating an amplifier for use with a sensor, two such goals are: low band pass corner frequency and low noise. Sensors such as magneto-resistive sensing elements require a direct current (DC) bias applied across them to operate correctly. The presence of such a DC bias may cause problems if the DC signal is passed on to amplifying elements. A low band pass corner frequency permits sensing of lower frequency signals while still rejecting DC signals and therefore contributes to a truer sensing of signals indicated by the sensor. Lower noise is desirable to reduce noise attributable to the sensor's read back signal.
Prior art signal amplifiers, especially signal amplifiers for use with a read head in an information storage device, have resulted in a compromise in noise performance when a very low band pass corner is needed.
There is a need for a signal amplifier apparatus that accommodates design for both low band pass corner frequency and lower noise.